1. Field of the Invention
The present invention relates generally to disk drives, and in particular to a disk drive suspension assembly including a shape memory actuator coupled to a gimbal.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base. The hub has an outer hub flange that supports a lowermost one of the disks. Additional disks may be stacked and separated with annular disk spacers that are disposed about the hub.
The head stack assembly has an actuator assembly having at least one transducer head (typically a magneto-resistive or “MR” head), typically several, for reading and writing data from and to the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
In further detail, the head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional “rotary” or “swing-type” actuator assembly typically includes an actuator having an actuator body. The actuator body is configured to rotate on a pivot assembly between limited positions about an axis of rotation. A coil support extends from one side of the actuator body. A coil is supported by the coil support and is configured to interact with one or more permanent magnets to form a voice coil motor. One or more actuator arms extend from an opposite side of the actuator body. To facilitate rotational movement of the actuator, the actuator assembly further includes the actuator body that has a bore and a pivot bearing cartridge engaged within the bore. Each magnetic disk includes opposing disk surfaces. Data may be recorded on a single surface or both along data annular regions. As such, the head stack assembly may be pivoted such that each transducer head is disposed adjacent the various data annular regions from adjacent the outer diameter to the inner diameter of each disk.
Conductive traces (formed of copper for example) are laid on a dielectric layer (such as a polyimide film) formed on the head gimbal assembly. The dielectric layer electrically insulates the conductive traces from the gimbal (which may be formed of stainless steel for example). Such technologies are variously named TSA (Trace Suspension Assembly), NSL (No Service Loop), FOS (Flex On Suspension) and the like. These conductive traces interconnect the elements of the transducer head to drive a preamp and the circuits associated therewith.
A typical suspension assembly includes a load beam (also referred to as a “suspension”) and a base plate (also referred to as a “nut plate” or “swage plate”). The base plate is used to attach the load beam to the end of the actuator arms, typically through a swage engagement. The suspension assembly further includes the gimbal supported at the end of the load beam. A hinge plate may also be utilized which is interposed between the load beam and the base plate. The suspension assembly with the slider attached to the gimbal is typically referred to as a head gimbal assembly.
The transducer head is disposed within the slider. The load beam has a spring function that provides a “gram load” biasing force and a hinge function that permits the head to follow the surface contour of the spinning disk. The load beam has an actuator end that connects to the actuator arm and a gimbal end that connects to the gimbal that carries the slider and transmits the gram load biasing force to the slider to “load” the slider against the disk. A rapidly spinning disk develops a laminar airflow above its surface that lifts the slider including the head away from the disk in opposition to the gram load biasing force. The slider is said to be “flying” over the disk when in this state.
As disk drives have progressed to higher areal densities, the fly height and the fly height tolerances has been correspondingly reduced. As such, the ability to maintain the slider within such operational specifications has become increasingly difficult. Accordingly, there is a need in the art for a disk drive having an improved suspension assembly design in comparison to the prior art.